A similar trimming pressure foot is known from Swiss Patent 541,650. In principle, the scissors connected to the pressure foot are actuated by the up-and-down motion of the needle drive rod. With each stitch of the needle, the scissors cut a short distance in front of the stitching point, in the direction of fabric feed. The cutting distance must be short enough to allow the path of the cut to follow a curve; and it must also be longer than the maximum possible stitch length of the machine. However, the stroke of the needle drive rod is very much longer than the required stroke at the movable blade of the scissors.
To enable easy replacement of the trimming pressure foot, the motion is derived from a part already present on the needle drive rod, specifically the needle securing screw. The stroke of the movable blade of the scissors should be only approximately one-tenth of the stroke of the needle drive rod. The trimming pressure foot known from Swiss Patent 541,650 requires a double lever translation to accomplish this. This makes the construction relatively complicated, difficult to use, and expensive to manufacture.